Method and apparatus for determining the position of an armature in an electromagnetic actuator by measuring the driving voltage frequency

• US 5,600,237 A
• Filed: 06/07/1995
• Issued: 02/04/1997
• Est. Priority Date: 11/29/1991
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Nippert, Andrew H.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/474,423
• Time in Patent Office: 608 Days
• Field of Search: 324/207.16, 324/207.24, 324/236, 324/652, 324/655, 324/654, 324/234, 324/681, 324/682, 324/707, 324/708
• US Class Current: 324/207.16
• CPC Class Codes: F16D 2048/0266 Actively controlled valves between pressure source and actuation cylinder
• CPC Class Codes: F16D 2500/1022 Electromagnet
• CPC Class Codes: F16D 2500/3022 Current
• CPC Class Codes: F16D 2500/3026 Stroke
• CPC Class Codes: F16D 2500/3028 Voltage
• CPC Class Codes: F16D 2500/7041 Position
• CPC Class Codes: F16D 2500/70418 Current
• CPC Class Codes: F16D 2500/7042 Voltage
• CPC Class Codes: F16D 48/06 Control by electric or electronic means, e.g. of fluid pressure
• CPC Class Codes: F16D 48/064 Control of electrically or electromagnetically actuated clutches F16D48/062, F16D48/068 take precedence
• CPC Class Codes: F16H 61/0251 Elements specially adapted for electric control units, e.g. valves for converting electrical signals to fluid signals
• CPC Class Codes: F16H 61/061 using electric control means
• CPC Class Codes: G01D 5/2006 by influencing the self-induction of one or more coils G01D5/22 takes precedence
• CPC Class Codes: G01R 27/2611 Measuring inductance
• CPC Class Codes: H01F 2007/1855 using a stored table to deduce one variable from another
• CPC Class Codes: H01F 2007/1861 using derivative of measured variable
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002

Abstract

Electromagnetic actuators having a coil and an armature are used in a number of applications in which it is useful to have an indication of the position of the armature with respect to the coil without the use of external sensors. Accordingly, an actuator control system is provided for determining the position of the armature with respect to the coil in response to the current magnitude and frequency of current flowing in the coil.

Claims

1. An apparatus for determining the position of an armature of an electromagnetic actuator having a coil, the armature being movable to and between first and second positions in response to current flowing through the coil, comprising:

means for applying a voltage to said coil to cause current to flow through said coil at a desired current magnitude;

means for measuring the frequency of said applied voltage; and

means for determining the position of the armature with respect to the coil in response to the applied voltage frequency and desired current magnitude.

2. An apparatus, as set forth in claim 1, wherein said position determining means includes a memory means for storing a plurality of positions corresponding to a plurality of applied voltage frequencies and desired current magnitudes, and responsively selecting one of said plurality of stored positions.

3. An apparatus for determining the position of an armature of an electromagnetic actuator having a coil, the armature being movable to and between first and second positions in response to current flowing through the coil, comprising:

means for applying a driving signal to said coil;

means for measuring the frequency of said driving signal and producing a voltage signal;

means for measuring the magnitude of current in the coil and producing a magnitude signal; and

means for receiving said magnitude and voltage signals, and responsively determining the position of the armature with respect to the coil.

4. An apparatus, as set forth in claim 3, wherein said position determining means includes a memory means for storing a plurality of positions corresponding to a plurality of magnitudes associated with the voltage and magnitude signals, and responsively selecting one of said plurality of stored positions.

5. A method for determining the position of an armature of an electromagnetic actuator having a coil, the armature being movable to and between first and second positions in response to current flowing in the coil, comprising the steps of:

applying a voltage to said coil to cause current to flow through said coil at a desired current magnitude;

measuring the frequency of said applied voltage; and

determining the position of the armature with respect to the coil in response to applied voltage frequency and desired current magnitude.

6. A method, as set forth in claim 5, including the steps of storing a plurality of positions corresponding to a plurality of applied voltage frequency and desired current magnitudes, and responsively selecting one of said plurality of stored positions.